1. Field of the Invention
The invention relates to a stamp unit having a holder member which is slidably disposed, in an axial, or up and down, direction within a skirt member and holds a stamp surface forming material at a lower end portion. A grip member is disposed on an upper portion of the holder member and moves the holder member downwardly. More specifically, this invention is a stamp unit having a transparent film which protects a stamp surface during transportation of the stamp unit, a period until a user starts to produce an original stamp plate using the stamp surface forming material after purchasing the stamp unit, and during production of the stamp plate. The transparent film is thermally adhered to a lower edge of the holder member, and is capable of protecting the stamp surface of the stamp material until the starting of stamp printing.
2. Description of the Related Art
Heretofore, several types of stamp units have been proposed. To focus on the method for producing a stamp plate used on such a stamp unit, stamp units will be classified into the following two groups. A type of stamp unit, for example, is disclosed in U.S. Pat. No. 5,483,880. Such a type of stamp unit has a grip portion, a stamp portion and a skirt member, the grip portion and the stamp portion are connected so that the stamp portion can be moved in an axial direction within the skirt member. A stamp material is installed covering the lower surface of an ink impregnated body. The stamp material comprises a thermal porous sheet having a porous substrate adhered to a thermoplastic film.
To produce a stamp plate capable of printing characters and images from the stamp material using such a stamp unit, the stamp unit is mounted on a stamp producing apparatus having a thermal head. The thermal porous sheet of the stamp material is perforated according to the desired characters by controlled heating of the thermal head, whereby the stamp plate is produced. After that, when printing characters and/or the image, if the grip portion is pressed downward under the condition that the stamp unit is disposed on a desired position of the printing sheet, ink impregnated by the ink impregnated body attaches to the printing sheet through the holes formed on the thermal porous sheet. Thereby, characters and/or the image can be printed.
A second type of stamp unit is described in European unexamined Patent-Application Publication No. EP 0 798 114, having a grip portion and a holder member. The holder member is connected to the grip portion. A stamp surface forming material is provided on the lower surface of the holder member.
The stamp surface forming material of the stamp unit comprises a porous resin layer. The porous resin layer is melted and solidified by being heated.
To produce this stamp surface forming material, a roll-shaped transparent film is transported within a stamp producing apparatus. As the film is transported, character and image data are printed thereon using a thermal head and an ink transfer ribbon to produce a positive copy of the desired stamp image. Then, the positive copy and the stamp surface forming material are set so as to oppose each other with a transparent acrylic plate provided therebetween. As the acrylic plate has higher melting point than that of the stamp surface forming material, when a light emitting member, such as a xenon tube or a laser light source, emits light under this condition, the lower portion of the stamp surface forming material is illuminated through the positive copy. Only the part of the lower portion of the stamp surface forming material, which is illuminated through the transparent portion of the positive copy, is melted and, as a result, solidified and sealed. The lower portion of the stamp surface forming material, which is neither melted nor solidified, remains as it is and is in the form of characters and the like of the desired image. Thereby, the stamp plate is produced on the stamp surface forming material. When the stamp unit is properly positioned, and the grip portion is pressed downward, the ink impregnated in the stamp surface forming material is exuded from the non melted-solidified portion and adheres to the printing sheet. Thus, the desired characters and/or image are printed.
In the second type of stamp unit, the stamp plate is directly produced on the stamp surface of the stamp surface forming material. Therefore, it is desirable to protect the stamp surface at the time of transportation of the stamp unit, during storage until a user starts to produce the stamp plate, and during production of the stamp plate. One way to protect the stamp surface of the stamp surface forming material would be to fix a protection film on the holder member. As one method to fix the protection film thereon, it is possible to provide an adhesive layer on the holder member and to adhere the film on the holder member. However, in such the case, there is a possibility that the adhesive layer has an adverse affect on the stamp surface of the stamp surface forming material. As a result, there is a problem that one cannot obtain an accurate stamp plate according to the positive copy. Therefore, up to the current time, the protection film is closely contacted with the stamp surface of the stamp surface forming material. However, the protection film is easily peeled off, because it is only closely contacted and it is not enough to protect the stamp surface of the stamp surface forming material.
Further, as a method to fit the stamp surface forming material with the holder member, it is common that the outer periphery of the stamp surface forming material is thermally adhered to the holder member using a thermal adhesion jig. However, the stamp surface forming material and the holder member include resin materials, so there is a problem that the resin materials adhere to the thermal adhesion jig at the time of thermal adhesion. In order to prevent adhesion to the thermal adhesion jig, measures are taken to specially treat the thermal adhesion jig, or to conduct the thermal adhesion with the intervening heat-resistant film between the stamp surface forming material and the holding member. However, to specially treat the thermal adhesion jig causes a jump in the stamp unit price, and to conduct the thermal adhesion with the intervening heat-resistant film between the stamp surface forming material and the holding member is complicated work, and prevents a smooth thermal adhesion.